The present invention generally relates to image pickup devices, and more particularly to an image pickup device capable of obtaining a fine color multiplexed signal even when irregularities in the pitch, color density, and the like exist in the striped filter. In order to correct the above irregularities, a voltage having a predetermined correction waveform is applied to a grid of an image pickup tube of the image pickup device.
Generally, as compared to a magnetic focus/magnetic deflection type image pickup tube, in an electrostatic focus/magnetic deflection type image pickup tube having a color striped filter, a focus coil on a deflection yoke can be eliminated, and the miniaturization of the image pickup camera is facilitated, hence often being used nowadays. However, the construction of the electrodes in the electrostatic focus type image pickup tube is complex compared to those of the magnetic focus type image pickup tube. Moreover, distortions in the electrodes of the image pickup tube are often introduced in many cases, and in these cases, irregularities are introduced in the color multiplexed signal of the video signal obtained. Accordingly, deleterious effects due to the above distortions in the electrodes were conventionally reduced by dynamic focusing in which the focus of the electron beam is varied according to the scanning position of the electron beam, to constantly obtain fine focusing.
However, in some cases, the color striped filter formed at the target of the image pickup tube has color irregularities and color density irregularities, due to the irregularities in the dye upon forming of the color striped filter, irregularities in the drying speed due to the position of the color striped filter upon drying of the color striped filter, and the like. Furthermore, there are cases in which pitch irregularities are introduced in the color striped filter formed, due to pitch irregularities in the mask for forming the color striped filter. When the above described irregularities in the color density, pitch, and the like exist in the color striped filter, irregularities are introduced in the color multiplexed signal of the video signal, and, as a result, color irregularities are introduced in the picture reproduced on the picture screen of the receiver. Moreover, in many cases, the above color density irregularities are continuously introduced at each filter stripe from the upper to lower end direction (that is, the vertical scanning direction).
The color irregularities due to the above various irregularities in the color striped filter could be reduced by the above dynamic focusing, however, the focus adjustment in the electron beam is rough by use of only the dynamic focusing, and fine adjustment sufficient to improve the color irregularities due to the above irregularities in the color striped filter, cannot be obtained. Accordingly, there was a limit in reducing the above color irregularities by the conventional method, and hence, the color irregularities could not be completely eliminated.